Expandable honeycomb structures have been used for many years as window coverings and are in some cases constructed of two separate pleated materials which are secured together either with or without additional materials so they define a plurality of longitudinally extending tubes or cells, one on top of the other. In the retracted state of the honeycomb structure, the adjacent cells are collapsed on each other. An example of such an expandable honeycomb structure is shown in the Anderson U.S. Pat. No. 4,685,986. Anderson forms the honeycomb structure by feeding previously pleated first and second sheets in opposite directions toward a pressure member. As the pleats approach the pressure member, one side of each pleat is covered with an adhesive and thereafter adjacent pleats in the first and second previously pleated sheets are pressed by the pressure member against two reciprocating folding knives and the resulting honeycomb structure is fed in a direction perpendicular to the direction of travel of the first and second pleated sheets.
While the Anderson method produces a satisfactory honeycomb structure it nevertheless is quite costly because it requires the use of previously pleated material.
According to the present invention, the problems noted above in forming expandable honeycomb structures have been ameliorated.